Disk drives store and retrieve data for digital electronic apparatuses such as computers. A typical magnetic disk drive comprises a head, including a slider and a transducer, in very close proximity to a surface of a rotatable magnetic disk. The transducer, in turn, includes a write element and/or a read element. As the magnetic disk rotates beneath the head, a very thin air bearing is formed between the surface of the magnetic disk and an air bearing surface of the slider. The write element and the read element can be alternately employed to write and read data while an actuator assembly positions the heads along desired magnetic “tracks” on the magnetic disk.
In order to keep the head properly oriented and at the correct height above the disk while in flight, disk drives employ a head gimbal assembly (HGA) that comprises the head and a suspension that further includes a load beam and a flexure that attaches the head to the load beam. The typical flexure is a layered structure that includes a thin metal support, electrical traces, and an insulating layer to keep the electrical traces from contacting the metal support. To electrically connect the head to the electrical traces during assembly, bonding pads of the head's transducer are connected to corresponding termination pads of the electrical traces on the flexure, for example by soldering.
One problem that arises during HGA assembly, when solder is used to connect bonding pads of the transducer to the termination pads on the flexure, is that the solder shrinks as it cools and solidifies. This creates a force that tends to pull the bonding pads and the termination pads towards one another. This force can cause the flexure to distort or solder bonds to fail, or both. A sufficiently distorted flexure may create a large enough pitch static angle (PSA) change in the orientation of the head that, when straightened during assembly, that an unacceptably high residual pitch torque adversely affects the height at which the head flies above the disk. Another problem that occurs is that PSA variation occurs due to different environmental conditions including both temperature and humidity changes.